You've currently got four rather large fish (for a ten gallon) sharing the same level of the tank. I'd suggest a larger tank for the barbs since they're better kept in a group, the bowl could be set up for the betta (they often have issues with dwarf gourami, you must have a pretty mellow gourami) and that would leave you with more room. If you aren't going to move anything out, you're probably best off waiting until you have a larger tank to stock more fish. I wouldn't do more shrimp with your current setup either since you have a shrimp eater in there somewhere.
With just the gourami and ADF in the tank, you should be able to easily get away with about five dwarf cories or three otos. If you have a sandy substrate, a group of 5 khuli loaches would also be an option, though you wouldn't see them as much as the cories. If you went with the oto option, you could probably also get away with a group of small tetras like neons, about five maybe? You may also be able to get away with a group of small tetras with the cories or loaches. I find that cories have great personalities, and little neons bring a great deal of color for a very small fish, just make sure you do groups of them so that they feel more secure and swim around for you. If you really don't want to move the betta, you could probably do a group of the bottom dwellers but no small tetras.
Don't know how your tank is decorated, but you can make it look a lot more busy in there by putting in some plants, small rocks and pieces of bogwood. I find it makes the tank look a bit more "full" and my fish are more active in well decorated tanks so there's more movement.
Hope that gives you some ideas! I have a ten gallon setup with a betta, four neons and an amano shrimp that all get along well, its much more difficult to stock the smaller tanks. I started out with a 25 gallon and an 80 gallon several years ago, now all my tanks are under 25 gallons and its much more difficult to work out stocking to get a nice balanced looking tank, it takes a lot more planning beforehand.